Detailed descriptions of communication networks and systems can be found in the literature. For example, detailed descriptions of mobile communication networks and systems can be found in Technical Specifications published by standardisation bodies such as for example 3GPP (3rd Generation Partnership Project), . . . etc.
Examples of mobile communication systems include GSM/GPRS, UMTS, CDMA 2000, 3G LTE, WiMAX, . . . etc.
As recalled in FIG. 1, in such systems, a mobile station or User Equipment (UE) has access via a Radio Access Network (RAN) to services provided by a Core Network (CN). Examples of Radio Access Network (RAN) include GERAN (for GSM/GPRS), UTRAN (for UMTS), ERAN (for 3G LTE), . . . etc.